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[ Care and Use ManUal ]

Waters Sep-Pak DNPH-Silica Cartridge 1

Contents

I. IntroduCtIon a. Sep-Pak DNPH-Silica Cartridge Description

II. usInG seP-PAK dnPH CArtrIdGes a. Theory of Operation

b. Preventing Contamination c. Collecting the Sample d. Eluting the Derivatives

III. AnALYZInG tHe dnPH derIVAtIVes a. Operating Guidelines

b. Performing HPLC Analysis c. Analyzing a Cartridge Blank

d. Selecting Separation Conditions

IV. APPLICAtIon eXAMPLes a. Estimating Sample Volume

b. Analysis of Auto Exhaust Emissions c. Analysis of Residential Air

d. Analysis of Research Lab Air

V. storAGe And dIsPosAL oF used CArtrIdGes

VI. trouBLesHootInG

VII. reFerenCes And BIBLIoGrAPHY

VIII. orderInG InForMAtIon APPendICes

IX. APPendICes a. Measuring Acetonitrile Purity

b. Synthesizing DNPH Derivative Standards c. Measuring Sample Breakthrough

I. IntroduCtIon

Waters Sep-Pak® DNPH-Silica cartridges are convenient, reproducible

sampling devices for quantifying aldehydes and ketones in gasses,

including air within a range of 1 to 5,000 parts per billion (ppbv).

WAters seP-PAK dnPH-sILICA CArtrIdGe



a. Sep-Pak DNPH-Silica Cartridge Description

• WatersSep-PakDNPH-Silicacartridgesconsistofacidified

2,4-dinitrophenylhydrazine-coated silica packed in Waters

Sep-Pak Plus cartridges.

• WatersSep-PakPluscartridgesareconstructedofhigh-purity

polyethylene components with triaxially-compressed packed

beds and Luer fittings equipped with end caps and plugs.

• Thegold-coloredaluminumcompressionringontheSep-Pak

DNPH-Silica cartridge allows for easy identification.

Figure 1: Cutaway View

Table 1: Physical/Chemical Properties

* Evaluate cartridge performance for individual high-temperature

methods.

Hold-Up Volume 0.7 mLParticle Size 55 to 105 µmCollection Efficiency >95% for sampling rates up to 2 L/minCapacity Approximately 75 µg formaldehydeQuantity of DNPH-Silica 0.35 g/cartridge (1.0 mg DNPH)Operating Temperature* 10 °C to 100 °CDimensions 4.3 cm total length

2.0 cm o.d. at widest point

1.0 cm i.d.

0.9 cm bed length

II. usInG seP-PAK dnPH-sILICA CArtrIdGes

a. Theory of Operation

Waters Sep-Pak DNPH-Silica cartridges trap aldehydes and ketones in

gasses by reacting them with the DNPH in the cartridge to form stable

hydrazone derivatives 1,2,3. The derivitization reaction (Figure 2) takes

place during sample collection. The derivatives are later eluted and

analyzed. Analysis should take place within two weeks.

Figure 2: Derivitization Reaction

b. Preventing Contamination

Contamination is most likely to occur during sample preparation.

Before eluting the derivatives, clean all glassware by rinsing with

acetonitrile and heating to 60 °C in a vacuum oven for at least

30 minutes. Eluting the samples in a nitrogen-purged glove box

further reduces the risk of contamination.

The acetonitrile used to elute the DNPH derivatives can also be a

source of contamination. Even HPLC-grade acetonitrile may have

unacceptable levels of carbonyl contaminants. A concentration of

10 µg/L of any aldehyde or ketone contaminant will add 0.1 µg to

the blank values determined for the DNPH derivatives per cartridge.

Follow the procedure in Appendix A to test your acetonitrile.

c. Collecting the Sample

Caution: Beware of unintentional exposure of the cartridges and

eluted samples to aldehyde and ketone sources. Laboratory air often

holds high concentrations of acetone. Labeling inks and adhesives as

well as packaging containers (including vials with plastic caps) are all

possible sources of contamination.

Polyethylene Filter

DNPH-Silica

Polyethylene Filter

Luer Connector

Aluminum Compression Ring

Luer Connector



The volume of air passed through the cartridge must be large

enough for the quantity of DNPH derivative formed to be several

times greater than the background level (Table 2). The United

States Environmental Protection Agency (US EPA) recommends

that this level be at least 10 times of that of the background3.

Figure 4 shows the ranges of sample volumes to use as a function

of expected concentration. If you can not predict the concentration

of total carbonyl compounds in a sample, follow the procedure in

Appendix C, Measuring Sample Breakthrough.

Table 2: Background Levels of DNPH Derivatives

* Individually, as acetone-DNPH, determined using a gradient

from 70/25/5 water/acetonitrile/tetrahydrofuran to 40/60 water/

acetonitrile. Other conditions are as in Section III, d.

Figure 4: Range of Sample Volumes vs. Expected Concentration

Caution: Ozone (usually present in urban air) degrades the hydrazone

derivatives4. Place an Ozone Scrubber Cartridge (Waters Part

number: WAT054420) on the inlet of the Sep-Pak DNPH-Silica

cartridge.

Notice: Do not use Sep-Pak DNPH-Silica cartridges to process liquid

samples.

To collect the sample:

1. Take the cartridge from its pouch. Remove and save the end cap

and plug.

2. Connect the cartridge to a pump with flexible plastic tubing.

The cartridge is bidirectional (flow can be in either direction).

Figure 3 shows the flow rate through a cartridge versus applied

vacuum.

3. Draw the sample through the cartridge. Record the flow rate and

collection time.

4. Reseal the cartridge with its end cap and plug.

5. Store the cartridge in the provided pouch with appropriate

identification. If possible, seal the pouch using a heat sealer,

or store the cartridge in a glass container with a Teflon®-lined

cap. Keep the samples cool (<4 °C). Elute the cartridge within

two weeks.

Figure 3: Flow Rate versus Applied Vacuum

Compound µg DNPH Derivative per Cartridge µg as Carbonyl Compound per Cartridge

Formaldehyde <1.0 <0.15Acetone <2.0 <0.50Others* <0.75 -



d. Eluting the Derivatives

There are two recommended methods for elution of the derivatives

from the cartridge:

Volumetric Method:

1. Elute the DNPH derivatives from the cartridge directly into a

5 mL volumetric flask. Use 3 mL HPLC-grade acetonitrile at a

flow rate of less than 3 mL/min. Higher flow rates (>3 mL/min)

can result in reduced recovery.

2. Dilute to volume with HPLC-grade acetonitrile.

Gravimetric Method:

1. Elute the DNPH derivatives from the cartridge directly into a

tared vessel. Weigh the eluate and divide by the density of the

acetonitrile to obtain the sample volume. Acetonitrile has a

density of 0.785 g/mL at 20 °C.

III. AnALYZInG tHe dnPH derIVAtIVes

a. Operating Guidelines

To ensure success in your HPLC analysis:

• Useapre-columnfilterbetweentheinjectorandcolumn.

• UseHPLC-gradeunstabilizedtetrahydrofuranformakingmobile

phases.

• UseHPLC-gradewaterandHPLC-gradeacetonitrile.

• Degasthemobilephasesbysimultaneouslyapplyingvacuum

and ultrasound to the mobile phases for 30 seconds. If you are

using a low-pressure mixing gradient system, sparging with

helium may be necessary.

• WatersNova-Pak® C18 columns are shipped containing

water/acetonitrile. Equilibrate the column at 1.5 mL/min for

10 minutes in mobile phase before the first analysis.

b. Performing HPLC Analysis

To analyze the sample:

1. Prepare the standard solution of the DNPH derivatives that you

need to quantify. The concentrations of the standards should be

in the same range as the expected concentrations in the sample.

To synthesize DNPH derivatives, see Appendix B.

2. Prepare a cartridge blank from the same sample lot as the

cartridge used to collect the sample, using the sample

procedure and same bottled solvent.

3. Analyze the standard solution to determine the response

factor for each derivative. Due to the high linearity of the

detector response, a single point calibration is sufficient for

Waters detectors.

Note: Use an injection volume appropriate for your column. Inject

≤20 µL for a 3.9 x 150 mm Nova-Pak C18 column, and ≤10 µL for a

3.0 x 75 mm Nova-Pak C18 column.

4. Analyze the cartridge blank to determine background levels.

Ensure that the blank values are in the normal range

(see Table 2).

5. Analyze the samples.

6. Subtract the blank values from the sample values. Run standards

at regular intervals between samples.

c. Analyzing a Cartridge Blank

Analyze a blank to determine background levels. Figure 5 shows a

typical result from a blank cartridge extraction. Since background

levels may change during storage (see Section V), always compare

samples to blank cartridges from the same lot stored under the same

conditions.

Note: When preparing a blank sample, ensure that you use the exact

bottled reagents that were used for the preparation of the sample.



To prepare a cartridge blank:

1. Elute a fresh DNPH-Silica Sep-Pak cartridge from the same lot as

the cartridges used to collect your sample.

2. Analyze the solution by HPLC using the same conditions as those

used for the sample.

3. Multiply the concentration of each DNPH derivative by the

volume of the eluate to determine the amount of background

DNPH derivative.

Figure 5: Typical DNPH-Silica Sep-Pak Cartridge.

d. Selecting Separation Conditions

Isocratic Separation of Derivatives

Use the conditions in Table 3 to separate DNPH and DNPH

derivatives of C1 through C3 aldehydes and ketones in less than

10 minutes. This separation requires a relatively weak mobile phase

(high water content) to separate the formaldehyde-DNPH derivative

from trace impurities. Figure 6 shows a representative chromatogram

using the isocratic conditions listed in Table 3.

Table 3: Isocratic Separation of C1-C3 Aldehyde and Ketone

Derivatives

Figure 6: Isocratic Separation of C1-C3 Aldehyde and Ketone

Derivatives

Gradient Separation of Derivatives

Use the gradient conditions listed in Table 4 to separate DNPH and

DNPH derivatives from a complex mixture of aldehydes and ketones

in 15 minutes. Figure 7 shows an example separation.

Table 4: Gradient Separation of C1-C9 Aldehyde and Ketone

Derivatives

Figure 7: Gradient Separation of C1-C9 Aldehyde and Ketone

Derivatives

Column Nova-Pak C18 3.9 x 75 mmMobile Phase Water/Acetonitrile/Tetrahydrofuran 65/30/5 v/vFlow Rate 1.5 mL/minInjectionVolume 10 µLDetection Adsorbance at 360 nm

1. DNPH2. Formaldehyde-DNPH3. Acetaldehyde-DNPH4. Acetone-DNPH5. Acrolein-DNPH6. Propionaldehyde-DNPH

Time (minutes)

Column Nova-Pak C18 3.9 x 150 mmMobile Phase A: Water/Acetonitrile/Tetrahydrofuran 60/30/10 v/v

B: Water/Acetonitrile 40/60 v/vGradient 100%Afor1min(adjustasnecessarytogivegradientdelay>

3mL) then a linear gradient from 100% A to 100% B in 10 minFlow Rate 1.5 mL/minInjectionVolume 20 µLDetection Adsorbance at 360 nm

Time (minutes)

1. DNPH2. Formaldehyde-DNPH3. Acetaldehyde-DNPH4. Acetone-DNPH5. Acrolein-DNPH6. Propionaldehyde-DNPH7. Crotonaldehyde-DNPH8. Butanone-DNPH9. Butyraldehyde-DNPH

10. Benzaldehyde-DNPH11. Isovaleraldehyde-DNPH12. Valeraldehyde-DNPH13. o-Tolualdehyde-DNPH14. m-Tolualdehyde-DNPH15. p-Tolualdehyde-DNPH16. Hexaldehyde-DNPH17. 2,5-Dimethylbenzaldehyde-DNPH

1. DNPH2. Formaldehyde-DNPH3. Acetaldehyde-DNPH4. Acetone-DNPH

Time (minutes)

1

1. DNPH2. Formaldehyde-DNPH3. Acetaldehyde-DNPH4. Acetone-DNPH

1

Cartridge Blank2 3 4

0 2 6 8 10 12 14



IV. APPLICAtIon eXAMPLes

a. Estimating Sample Volume

An expected formaldehyde concentration in a paper mill is estimated

to be 1000 ppbv. Refer to Figure 4 to find the sample volume to

collect. For this example, a sample volume of 10 liters is sufficient.

The pump used in this example generates 17 inches (Hg) of vacuum,

resulting in a flow rate through the cartridge of 2 L/min. Therefore,

five minutes of pumping at 2 L/min yields the 10 liter sample

required for the analysis.

b. Analysis of Auto Exhaust Emissions

A typical analysis of diluted exhaust emissions from car fueled by

gasoline is shown in Figure 8. The sample* was collected using a

constant volume sampler dilution tunnel. The car was operated on a

prescribed driving schedule on a chassis dynamometer.

The cartridge was connected to a heated (100 °C) sampling manifold

using a short piece of Teflon tubing. The sample was collected using

a metal bellows pump and a mass flow controller.

Figure 8 represents an 8.4 liter sample collected at 1 L/min.

Formaldehyde is the most abundant carbonyl compound emitted

(ca. 2000 ppbv). Smaller amounts of other aldehydes and ketones

also appear.

* The sample was provided by Dr. S.B. Tejada of the US EPA

Atmospheric Research and Exposure Assessment Laboratory.

Figure 8: Analysis of Auto Exhaust Emissions

Time (minutes)

1. DNPH2. Formaldehyde-DNPH3. Acetaldehyde-DNPH4. Acetone-DNPH5. Acrolein-DNPH6. Propionaldehyde-DNPH7. Crotonaldehyde-DNPH8. Butanone-DNPH9. Butyraldehyde-DNPH10. Benzaldehyde-DNPH11. o-Tolualdehyde-DNPH12. m, p-Tolualdehyde-DNPH13. 2,5-Dimethylbenzaldehyde-DNPH

c. Analysis of Residential Air

An example of an analysis of indoor air in a conventional home is

shown in Figure 9. A 108 liter sample was collected at 0.6 L/min

using a portable sampling pump. The chromatogram shows

formaldehyde (31 ppbv), acetaldehyde (9 ppbv), acetone (62 ppbv),

and hexaldehyde (2 ppbv).

Figure 9: Analysis of Residential Air

d. Analysis of Research Lab Air

The sample in Figure 10 was collected in a chemical research labora-

tory using a portable sampling pump. A 100 L air sample was drawn

through the cartridge at flow rate 0.65 L/min. The chromatogram

shows formaldehyde (4.8 ppbv), acetaldehyde (1.2 ppbv), acetone

(118 ppbv), butanone (0.8 ppbv), and isovaleradehyde (0.7 ppbv).

Figure 10: Analysis of Research Lab Air

Time (minutes)

Lab Air Sample

Cartridge Blank

1. DNPH2. Formaldehyde-DNPH3. Acetaldehyde-DNPH4. Acetone-DNPH5. Butanone-DNPH6. Isovaleraldehyde-DNPH

Time (minutes)

Residential Air

Cartridge Blank

1. DNPH2. Formaldehyde-DNPH3. Acetaldehyde-DNPH4. Acetone-DNPH5. Hexaldehyde-DNPH



VI. trouBLesHootInG

Use Table 5 to solve common problems that may arise while using

the cartridges. Most errors occur as a result of contamination during

sample preparation. If resolution problems persist, validate the HPLC

system5.

Table 5: Troubleshooting Common Problems

VII. reFerenCes And BIBLIoGrAPHY

1. Committee on Aldehydes, Board of Toxicology and

Environmental Hazards, National Research Council,

Formaldehyde and Other Aldehydes; National Academy Press,

Washington, DC, 1981.

2. Tejada,S.B.,“EvaluationofSilicaGelCartridgesCoatedIn

Situ With Acidified 2,4-Dinitrophenylhydrazine for Sampling

Aldehydes with Ketones in Air”, Intern. J. Environ. Chem. 1986,

26, 167-185.

3. Riggins,R.M.,“CompendiumofMethodsfortheDetermination

of Toxic Organic Compounds in Ambient Air”, US Environmental

Protection Agency Report EPA-600/4-84-041, US

Environmental Protection Agency: Research Triangle Park, NC,

1984.

V. storAGe And dIsPosAL oF used CArtrIdGes

Storing unused Cartridges

Always store any unused Waters Sep-Pak DNPH-Silica cartridges in

their protective pouches to prevent contamination.

Store the sealed pouches in a refrigerator at (4 °C or lower) for up to

six months. Cartridges may be stored in their unopened pouches at

room temperature (20 to 25 °C) for up to two weeks.

Background levels of hydrazone derivatives increase slightly with

time and temperature. Before using cartridges exposed to high

temperatures or stored longer than the recommended periods, run a

blank.

Storing Exposed Cartridges

Once a cartridge has been used to collect a sample, be careful to

cap and seal it until it is time to elute it. Inadvertent exposure of an

exposed cartridge can ruin a carefully collected sample. Elute the

derivatives from the cartridge within two weeks.

Disposing of Used Cartridges

Dispose of used cartridges according to applicable government

regulations.

Symptom Possible Cause SolutionHigh carbonyl values in unused cartridges

Contaminated acetonitrile Certify acetonitrile quality prior to use, see Appendix A

Contaminated glassware Use only pre-cleaned glassware.Air contamination of sample during elution

Prepare sample in a glove box.

Cartridge age and storage conditions

Buy new cartridges. Refrigerate unused cartridges. Rotate stock.

Improper mobile phase composition

Prepare fresh mobile phase, decrease acetonitrile content.

Formaldehyde coelutes with other peaks

Separation conditions Check separation conditions. Use a gradient separation.

Broad peaks Injectionvolumetoohigh Useinjectionvolumeappropriateto column (≤ 20 µL for 150 mm or ≤ 10 µL for 75 mm Nova-Pak

C18 columns).



4. Arnts,R.R.andTejada,S.B.,“2,4-Dinitrophenylhydrazine-

Coated Silica Gen Cartridge Method for Determination of

Formaldehyde in Air: Identification of an Ozone Interference”,

Environ. Sci. Technol. 1989, 23, 1428-1430.

5. Guide to Successful Operation of Your LC System; Millipore

Corporation, Waters Chromatography Division: Milford, MA

1991. See Appendix E to order.

6. ASTM Method E411; Standard Test Method for Trace Quantities

of Carbonyl Compounds with 2,4-Dinitrophenylhydrazine.

VIII. orderInG InForMAtIon

Waters Sep-Pak DNPH-Silica cartridges are shipped in boxes of 20

individually-packaged cartridges. Pouches are supplied for storage

after sampling.

Table 6: Ordering Information

IX. APPendICes

Appendix A: Measuring Acetonitrile Purity

HPLC-grade acetonitrile may contain traces of aldehydes and

ketones, especially acetone. 10 µg/L of an aldehyde or ketone

in the acetonitrile adds 0.1 µg DNPH derivative per cartridge to

background values.

If your acetonitrile is unacceptable for your application, contact your

solvent supplier, or purify the acetonitrile. To purify acetonitrile,

distill it from an acidified DNPH solution using a procedure

analogous to the one described in ASTM Method E411 for the

purification of methanol6.

To measure acetonitrile purity:

1. Clean all glassware by rinsing with acetonitrile and heating in a

60 °C vacuum oven for at least 30 minutes.

2. Elute a fresh cartridge with 3 mL acetonitrile.

3. Within3minutes,injecttheeluateontotheHPLCsystemto

measure the concentration of DNPH derivatives.

4. Add 1 drop of concentrated HCl to the eluate and allow it to

react at room temperature for 30 minutes.

Derivative Concentration (µg/mL)Formaldehyde-DNPH 0.08Acetaldehyde-DNPH 0.12Acetone-DNPH 0.40All other hydrazones <0.05

Derivative Concentration (µg/mL)Formaldehyde-DNPH 0.09Acetaldehyde-DNPH 0.14Acetone-DNPH 2.00All other hydrazones <0.05

Derivative Concentration after Reaction

with Acid

Minus Concentration in

Blank

Equals Contribution from

AcetonitrileFormaldehyde-DNPH

0.09 µg/mL - 0.08 µg/mL = 0.01 µg/mL

Acetaldehyde-DNPH

0.14 µg/mL - 0.12 µg/mL = 0.02 µg/mL

Acetone-DNPH 2.00 µg/mL - 0.40 µg/mL = 1.60 µg/mL

Derivative Contribution from

Acetonitrile

Divided by Background

Value

Times 100 Equals Percent Relative to Background

Formaldehyde-DNPH

0.01 ÷÷ 0.08 x 100 = 12%

Acetaldehyde-DNPH

0.02 ÷÷ 0.12 x 100 = 17%

Acetone-DNPH 1.60 ÷ ÷ 0.40 x 100 = 400%

Product Part NumberSep-Pak DNPH-Silica Cartridges, 20/box

WAT037500

Sep-Pak DNPH-Silica Long Body Cartridges, 20/box

WAT039550

Nova-Pak C18 Column, 3.9 x 75 mm WAT011670Nova-Pak C18 Column, 3.9 x 150 mm WAT086344In-line Pre-Column Filter (0.5µm) 600000180HVLP Mobile Phase Filter, 100/pkg WAT200530Beginners Guide to Liquid Chromatography

715001531

Ozone Scrubber Cartridge, 20/box WAT54420



5. Remeasure the concentration of DNPH derivatives by HPLC.

6. Calculate the difference in the concentration of each DNPH

derivative measured in steps 3 and 5 to yield the contribution

from the acetonitrile.

7. Calculate the percent hydrazone contributed by the acetonitrile

relative to the background level. The value for any hydrazone

should not exceed 25% of its value in the blank.

Example: Measuring Acetonitrile Purity

1. HPLC analysis of a fresh cartridge shows the sample contains:

2. Analysis of the concentrations of hydrazones after reacting with

acid yields:

3. The different between the concentrations of hydrazone from

steps 3 and 5 represent the amount of hydrazone contributed by the

acetonitrile.

4. The percent of the hydrazones contributed by the acetonitrile are:

Since the percent for formaldehyde and acetaldehyde arising from the

acetonitrile is less than 25% of the background level in the cartridge,

the acetonitrile is considered clean for these compounds. If the analysis

considers only these compounds, the acetonitrile is acceptable.

However, the amount of acetone arising from the acetonitrile is four

times the amount in the blank (much higher than the 25% suggested

maximum). Therefore, it is suggested that this lot of acetonitrile may

be unacceptable for the analyses.

Appendix B: Synthesizing DNPH Derivative Standards

DNPH-derivative standards are easily synthesized from DNPH supplied

by Aldrich Chemical Co. (70% DNPH and 30% water). To synthesize

98-99% pure hydrazones:

1. Prepare one liter of 2 M HCl solution: Add 172 mL concentrated

reagent-grade hydrochloric acid (HCl) to a 1 L volumetric flask.

Fill the flask to the mark with distilled deionized water.

2. Saturate the 2 M HCl solution with DNPH: Add 8 g DNPH and stir

for one hour at 20 to 25 °C. Filter through a 0.45 µm hydrophilic

membrane (HVLP) filter (Waters Part number: WAT200530).

3. Form hydrazone derivative: Add a two-fold molar excess of

reagent-grade aldehyde or ketone to the filtered 2 M HCl DNPH

solution. Stir for 30 minutes to one hour at 20 to 25 °C.

4. Filter the hydrazone slurry. Wash the hydrazone with 50 mL 2 M

HCl 3 times. Wash with 50 mL water 3 times. Dry the filter cake

in an oven at 50 to 60°C overnight.

5. Prepare standard solutions in acetonitrile at concentrations

between 1 to 10 mg hydrazone/L. The solutions are stable for

at least one month when stored in tightly-capped glass vials

at 4 °C.

Appendix C: Measuring Sample Breakthrough

Note: If several aldehydes and ketones are present in significant

concentration, estimate the maximum sample size from the total

concentration of all species.

The collection efficiency for Waters Sep-Pak DNPH-Silica cartridges is

greater than 95% for gaseous sampling rates of up to 2 L/min. The

sample may exhibit breakthrough if:

• Thesamplingflowrateisgreaterthan2L/min

• Theamountofsamplecollectedisenoughtoreactwithmore

than 50% of the DNPH (equivalent to 0.5 mg DNPH)

To measure DNPH-Silica cartridges for collection efficiency:

1. Connect two unused cartridges together by the Luer fittings and

mark each cartridge for identification.

2. Connect the cartridges to a pump with a short length of flexible

tubing.

3. Collect the sample.

4. Elute both cartridges and an unused third blank cartridge.



5. Analyze all three cartridges by HPLC.

6. Subtract the value from the blank cartridge from the values

determined from the other two cartridges.

7. Calculate and sum of the total captured DNPH-derivative from

both cartridges 1 and 2.

8. Divide the amount of DNPH-derivative determined from the first

cartridge by the total amount determined form cartridges 1 and

2. Multiply by 100. This is the percentage of DNPH-derivatives

captured on the first cartridge. This value should exceed 95%

otherwise, some of the sample broke through to the second

cartridge.

Example: Measuring Sample Breakthrough

To measure breakthrough:

Expected concentration of formaldehyde is 500 ppbv. Flow rate is

2.0 L/min. A sample volume if 100 liters yields:

Analyte ppmv Carbonyl Collectedconcentration x molecular x air volume = µg Carbonyl weight

Analyte molar volume at 1 atm/25 °C

This calculates to:

0.66 µL x 30.03 g/mole x 100 L = 81 µg formaldehyde

24.46 L/mole

The actual results are shown in Table 7. To calculate the percent

captured on the first sampler, divide the quantity captured on sampler

1 by the total quantity captured, then multiply by 100. Since this

value is less than 95%, and the total carbonyl amount exceeded

2.3 µmoles, breakthrough occurred.

Table 7: Breakthrough Example HPLC Results

In the above example, only a single carbonyl source was present.

Under many test conditions more than one carbonyl source may be

present in significant concentrations. These other compounds will

consume DNPH, effectively reducing the capacity of the sampler for

the compound of interest. To assure that the capacity of the sampler

has not been exceeded, compare the DNPH peak areas of the sample to

a similarly eluted blank. The DNPH peak area in all samples must be

no less than 50% of the DNPH peak area of the blank. This ensures

the sampler capacity has not been exceeded.

Sampler Amount (µg) Quantity Captured

Sampler – blank (µg)

Percent Captured on Sampler

Sampler 1 75.06 75.00 91.8Sampler 2 6.72 6.66 8.2Blank 0.06 - -



Waters Corporation 34 Maple Street Milford, MA 01757 U.S.A. T: 1 508 478 2000 F: 1 508 872 1990 www.waters.com

© 2009 Waters Corporation. Waters, The Science of What’s Possible, Sep-Pak and Nova-Pak are trademarks of Waters Corporation.

March 2009 WAT037506 Rev B KK-PDF

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